Transcript The Diversity of Life

Change Over Time
Evolution: Change Over Time

Age of earth 4.55 billion years (rocks dated on
earth 3.8 to 3.9 billion by decay of their
radioactive elements)
 Life began 3.9 to 4.1 billion years ago
 Life forms have evolved over a long period of
time
 Great diversity of life, how did it arise how are
things related?
Evidence-Organisms have changed over
time
Fossil Record- Organism is preserved (pg 382
and 417)
Paleontologist:
Scientist that studies fossils
What does the fossil record show?
The history of life on Earth, how different
organisms have changed over time
Extinct:
Species die out (99% of all species has died out)
 Rock- Only hard parts of the organism are
preserved for example bones; it is buried under
layers of sediment. The minerals in the bones,
calcium and hydroxyapatite, get replaced, one by
one, with the minerals in the sediment.
1.
Evidence of Change Over Time
 Fossil
Record
Tyrannosaurus rex 68-65 mya
Archeopteryx 150-145 mya
Trilobites 17,000 species from 540-250 mya
marine arthropods
 Q.
What type of rock do fossils usually
occur in?
 Sedimentary rock
 Q. Give an example of an organism
whose history is written in stone
 The horse
 Q. Where in the earth’s layers of rock
would you expect to see the oldest life
forms?
 In the lower layers (bottom)
Can see a change in life forms in the different
layers of rock
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The fossil record is incomplete; it does not show
every step in the evolution of earth’s life forms.
Q. Suggest reasons why this is the case.
 Not all organisms have hard parts.
 Location, sediment and other conditions
have to be present to form a fossil.
 Exposure of fossil sites
Dating Fossils
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Relative: Estimate a fossils age by comparing
its position in the rock layers compared to other
fossils (index fossils)
Index Fossil: easliy recognised, large range but
short time period on Earth
Radioactive dating: use of radioactive decay of
certain elements. Decay is at a known constant
rate known as a half-life
Uranium-235 decays to lead 207 half-life is 700
mya
Potassium-40 to argon-40 half-life = 1.26 billion
years
Carbon-14 to carbon-12 half life 5 568 yrs
Frozen- Organism has
to be frozen quickly
before any tissues
start to decay.
 For example Iceman
found in the Alps in
1991 was 5300 years
old.

Amber- Organism
gets caught in resin of
ancient trees usually
conifers, which then
hardens to fossilize
them

Using your text book research evidence that
supports evolution, for each provide a
description.
 2. Biogeography
3. Comparative Anatomy
 Study of the organisms structure
 Scientists compare similarities and differences in
organisms structure.
 Homologous structures have similar functions
and origins, but are seen in different forms.
 Their similarities suggest a common (shared)
ancestor.
 The differences are due to the different
evolutionary paths, structures evolved to suit
different environments and adapt that animal to
a particular way of life.
Homologous Structures
Vestigial Structures
4. Comparative Embryology

Comparing and contrasting the embryos of
different organisms.
 Show relationships between species not always
seen in the adult.
 Pig and human inherited the same basic body
plan from a common ancestor.
Embryology
5. Molecular Biology

Studies on a biochemical level, for example the
structure of blood proteins hemoglobin are very
similar in the human and the chimpanzee. The
amino acid sequences are almost the same.
Human and chimpanzee shared a common
ancestor
 Analyzing similarities in DNA and RNA
sequences (genes)
 Genes are a basis for change.
 Rise of new alleles and genes by mutation give
rise to new proteins, which enable an organism
to change. A process of evolution.
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 Molecular
Clock